SOLID & Design Patterns Interview Question #73

What is a Domain Service?

Advanced Patterns, CQRS & Domain-Driven Design Fundamentals Mid-Level Intermediate

Quick Interview Answer

A Domain Service contains domain behavior that does not naturally belong to a single entity or value object. It expresses business logic using domain concepts and should remain focused on the domain rather than infrastructure concerns.

Detailed Explanation

For example, a pricing calculation involving several domain objects may belong in a domain service when placing it on any one entity would distort that entity's responsibility.

Code Example

public class PricingService
{
    public Money Calculate(
        Customer customer,
        Order order,
        PricingPolicy policy)
    {
        // Domain calculation.
        return new Money(0m, "USD");
    }
}